US boffins hail lab-grown rabbit todger

Repaired lapines going at it like, erm...

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US researchers have offered long-term hope to human sufferers of erectile disorder by restoring "sexual function" to rabbits with damaged penises.

The team from the Institute for Regenerative Medicine at Wake Forest University Baptist Medical Center grew new penile tissue in the lab. They implanted it into their lapine guinea-pigs and reported they were thereafter once more going at it like er, rabbits.

Specifically, the scientists "extracted smooth muscle cells and endothelial cells" from the animals' members. The former "relaxes, allowing blood to flow into the penis" during an erection, while the latter "line blood vessels [and] trigger the process by releasing nitric oxide".

Healthday Newsexplains: "The cells were then separated and grown in the laboratory on rod-shaped collagen scaffolds for support. The scaffold was placed in an incubator and nourished by fluids to mimic conditions inside the body.

"After the cells had matured, the scaffolding and the newly formed penile spongy tissue, called corpora cavernosa, was surgically implanted into the rabbits' penises."

A month later, "the tissue began to reconstitute itself, forming new blood vessel structures necessary for proper functioning... while nerves from the existing penile tissue integrated into the new tissue".

Subsequent tests showed that that "pressure inside the penis, blood flow, response to nitric oxide, drainage of the blood after the erection and presence of sperm in the female vagina were also normal".

So normal, in fact, that four of a dozen female rabbits on hand to assist the study were impregnated by the reinvigorated males.

Dr Anthony Atala, lead author of the study which will appear in Proceedings of the National Academy of Sciences, said: "We were able to show the tissue was able to integrate and function in the long term, which means we can start planning clinical applications [in humans].

"Our hope is to be able to treat patients with many conditions, including congenital abnormalities of the penis, traumatic injuries, penile cancer and severe cases of erectile dysfunction that don't benefit from drug treatments."

Dr Andrew McCullough, director of male sexual health, fertility and microsurgery at NYU Langone Medical Center, called the results "promising". He said: "It has a long way to go, but the researchers have basically shown they can take cells from an organ, culture them, put them back in and have them be functional.

"This is especially impressive because the penis is an organ that's a very sensitive hydraulic pump, so to speak. During an erection, blood has to flow into the organ. The organ then has to expand and then shut down the drainage so the blood doesn't flow back out. And all of these things are very interrelated."

McCullough concluded that better treatments for erectile dysfunction were a matter of priority for the 35 per cent of affected men who "don't respond to impotence drugs, including Viagra, Cialis and Levitra". ®